1. Field of the Invention
This invention relates to incendiary devices and methods used to initiate fires, more specifically, for the purpose of igniting prescribed fires in forest and range land vegetation.
2. Description of the Related Art
Prescribed burning refers to the deliberate application of fire to wildlands to achieve specific resource management objectives. It involves the tasks of planning, igniting and controlling the fire. Known fire behavior models are used to determine the range of weather conditions that will permit accomplishment of sufficient fuel reduction goals, while still allowing personnel to maintain control of the fire. Burning operations can only be conducted when fuel moistures are within a specified range, and weather conditions must be ideal in order to produce a desirable level of fuels reduction with minimal risk of fire escape. Air quality is a significant concern, which may limit the time frames available for conducting burn projects. Limited available personnel and limited funding further hamper the ability of resource management personnel to meet their prescribed burning goals.
The two operational phases of prescribed burning are the ignition phase and the holding phase. The holding phase involves controlling a fire that has been set, and this phase is highly dependent on the availability of manpower and equipment. The present invention relates to the ignition phase. Currently, there are two primary means of ignition: aerial ignition and ground ignition. Aerial ignition involves the use of helicopters to fly over the intended burn area and dispense either incendiary plastic spheres (as in U.S. Pat. No. 4,422,383) or a trail of flaming, gelled gasoline (as in U.S. Pat. No. 4,247,281). Helicopter use is very costly and requires a number of ground support personnel; however, it is the preferred method for treating large burn areas. There is a higher level of risk to personnel involved with aerial operations, and there is a limit to the level of precision that can be achieved with aerial ignition.
Handheld drip-torches, which have been used for decades, are the predominate tool used for ground ignition. This method involves personnel walking across unburned fuels, in sequential strips through the burn unit, while dispensing a flaming diesel/gasoline mix. Depending on vegetation conditions, this process can be extremely time-consuming or, alternatively, may require a significant number of ground personnel. Crew safety is also an obvious concern, as personnel are setting fire to materials through which they are walking. In short, the primary method of igniting natural fuels, whether by aerial or ground means, is the application of flaming petroleum products to the natural fuels.
By contrast, the present invention involves an improved method for the ignition of natural vegetative fuels that does not rely on the application of flaming petroleum products. Instead, the present invention is a filamentous incendiary material that will ignite rapidly and sustain sufficient flaming combustion for the ignition of forest fuels.
The prior art includes a number of patents and published applications directed toward various methods of igniting fires, but none of these inventions possess the unique attributes of the present invention, which are more fully described below. Much of the prior art relates to fuses, which are distinguishable from the present invention. A fuse is defined generally as a core of readily combustible material that is lighted at one end to carry a flame along its length to detonate an explosive at the other end. Whereas a fuse works to transmit a signal (or flame) along its path from one point to another, the present invention is intended to ignite quickly (nearly instantaneously along its length) and sustain flaming combustion for a period of time sufficient to ignite wood, grass, straw, needles, moss, and any other type of fuel that is in close proximity along the length of the strand of the present invention.
The prior art also includes deflagrating cords that ignite instantaneously and provide a short-lived flash of heat sufficient to ignite a rocket motor or vehicle air bag deployment charge. Unlike the present invention, these deflagrating cords do not provide the duration of flaming combustion necessary to light vegetative materials that may have a high moisture content. For this reason, the deflagrating cords that have been described in previous patent applications are not as effective as the present invention in igniting forest vegetation.
There are several examples of the fuse-type ignition method. U.S. Publication No. 2002018941 (Smith, 2002) discloses a linear ignition fuse with a shaped sheath that creates gas channels along the length of the fuse; U.S. Pat. No. 4,220,087 (Posson, 1980) describes a linear ignition fuse with a gas channel that extends longitudinally; and U.S. Pat. No. 5,540,154 (Wilcox et al., 1996) provides a linear ignition fuse with an elongated core of non-detonating ignitive material, a longitudinally extending gas channel, a frangible sheath of inorganic material surrounding the core and the channel, and a jacket of braided filaments encasing the sheath. U.S. Pat. No. 5,540,155 (Hill, 1996) relates to an elongate flexible fuse made of an oxidizing agent and a fuel present in quantities that allow for a rate of burning of from 10 seconds/meter to 250 seconds/meter.
There are also a number of patents that cover deflagrating cords. Some examples are: U.S. Pat. No. 3,320,882 (Schulz, 1967), which discloses an igniter cord consisting of a high explosive compound and a particulate metal enclosed in a metal sheath, for use in connection with propellant charges and rocket ignition; U.S. Pat. No. 5,322,018 (Hadden et al., 1994), which describes a surface-initiating deflagrating material consisting of a pyrotechnic material and an inorganic binder, such as silica, carried on a carrier web preferably made of fiberglass and with a hollow core; and U.S. Pat. No. 3,367,266 (Griffith, 1968), which relates to a detonating and deflagrating fuse that has a wrapper of flexible material enclosing a cracked and discontinuous column of solid explosive.
Several patents have attempted to deal with the specific problems associated with fire ignition for the purpose of agricultural practices, forest management, or amelioration of environmental contamination. U.S. Pat. No. 4,256,086 (Collett et al., 1981) covers a method for rapidly igniting combustible material over a predetermined area of a field. Simply put, this method involves attaching combustible elements to a line and advancing the line across the field. U.S. Pat. No. 4,247,281 (McGrew et al., 1981) describes a method of “slash burning” whereby a helicopter carries a dispenser with a jelly-like mixture of aluma gel and gasoline, and the mixture is ignited and dropped on the area to be burned. U.S. Pat. No. 5,429,494 (Kuehn, 1995) discloses a transportable ignition device adapted for use in forestry management practices and consisting of a fuel storage tank and a pressurizing assembly. The fuel is expelled from an application wand, ignited, and delivered to a distant target by virtue of the pressurized pump. U.S. Pat. No. 4,422,383 (Couture et al., 1983) relates to a floating incendiary device that is dropped from an aircraft onto a combustible material on a body of water. The device includes an incendiary composition that is sandwiched between a pair of discs that direct the resulting flame radially outwardly over the surface of the combustible material. The latter invention was intended to provide a method for dealing with hydrocarbon slicks that float on water and adversely affect the marine environment. U.S. Pat. No. 6,128,845 (Jacobson, 2000) relates to a fire starting flare for hand-held launchers that allows brush fires to be started remotely from the person controlling the device. The flare projectile of the invention has a range of one hundred thirty yards and emits a shower of sparks over the immediate vicinity of where it lands.
The main object of the present invention is to provide a method of igniting fires for the management of forest vegetation that is much safer for fire management personnel than the primary method currently employed, which entails dispensing flaming petroleum while walking through the area to be burned. A further object of the present invention is to provide a method for fire ignition that is more effective in igniting forest vegetation than the fuse- or deflagrating cord-type methods described above.